Footwear with improved tightening of upper

ABSTRACT

An article of footwear, such as a boot, including an outer sole assembly and an upper, the boot extending lengthwise from a heel to a tip, widthwise between a lateral portion and a medial portion, and heightwise from the outer sole assembly to an upper end, the boot having an opening for inserting the foot, and including a reinforcement which is integral with the upper and is more rigid than the remainder of the upper, at least in the region of the instep, the reinforcement including a lateral and/or a medial edge extending over a reduced length of the boot at least plumb with the instep, the boot including a transverse linkage provided to tighten the instep zone, the linkage extending from the lateral portion to the medial portion. The linkage includes a first subdivision extending in the longitudinal direction of the boot, over a distance between 25% and 70% of the length thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon French patent application Ser. No. 11/03080, filed Oct. 11, 2011, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is claimed under 35 U.S.C. §119.

BACKGROUND

1. Field of the Invention

The invention relates to an article of footwear, especially a sports boot, and relates more particularly to a boot adapted for skiing, power walking, and other sporting activities.

A boot of the aforementioned type can be used in fields such as cross-country skiing or telemark skiing, walking or running on flat or mountainous terrain, hiking, snowboarding, snowshoeing, roller skating, skateboarding, cycling, ball sports, and the like.

2. Background Information

A boot can have a low upper or a high upper. It is generally desirable for the foot of a user to be adequately supported. Indeed, good foot support in the upper results in a more efficient use of the boot.

For example, adequate support in a flexible boot, such as that in a boot used in cross-country skiing, facilitates the transmission of sensory information and the rolling movement of the foot during use. A device for tightening the upper is adapted to support the user's foot, especially in the area of the instep.

Conventionally, a tightening device includes a linkage, such as a lace, on the one hand, and guides for connecting the lace to the upper. These guides or connections are defined by keepers, e.g., that are associated with lateral and medial portions or quarters of the upper. The lace follows a path along which it runs alternately from one quarter to the other. Thus, it suffices to pull on the lace to bring the quarters in a direction toward one another to tighten the upper. Thereafter, blocking the lace keeps the upper tightened.

An objective that a good tightening device must achieve is holding the foot within the boot. In particular, when skating, i.e., cross-country skiing with skating steps, it is important to hold the foot adequately in a transverse direction of the boot, which enables a wearer to exert a more precise transverse thrust. Thus, undesired movements of the foot within the boot, especially in the area of the instep, are to be avoided.

Indeed, when the foot moves within the upper, in the area of the instep or elsewhere, the sensory information or steering forces are transmitted less precisely. Consequently, performance, especially in sports, but also walking or running generally, is adversely affected. Moreover, repeated foot movements in the upper can result in friction that causes injury to the foot.

To improve foot support, providing the boot with a reinforcement that is integral with the upper and is more rigid than the remainder of the upper, at least in the region of the instep, has been proposed.

Such an example is disclosed in the document FR 2 923 362 and in family member document US 2009/0119952, in which a boot includes a conventional tightening device, i.e., one having a lace and keepers arranged to tighten the upper reversibly, but also a rigid reinforcement including a lateral wall and/or a medial wall. The reinforcement extends over a reduced length of the boot, at least plumb with the instep. The boot according to the documents FR '362 and US '952 includes a transverse linkage provided for tightening the instep zone, such linkage extending from the lateral portion to the medial portion. The linkage adds a tightening force to that exerted by the device. As a consequence, the foot is more tightly held in the area of the instep and/or in the area of the metatarsus. This means that the foot is biased toward the outer sole assembly with greater force.

However, a boot according to the documents FR '362 and US '952 has shown that foot support and/or comfort are sometimes incomplete. In particular, undesired movements of the foot are still observed in the upper, in the area of the tarsus or in the area of the metatarsus, in the transverse direction and/or in the vertical direction. These movements cause user fatigue, because the user must overexert to transmit forces. More broadly speaking, the transmission of sensory information can be said to be incomplete.

In other words, it is still desirable to improve foot support, especially transverse support or vertical support, or both at once, in a boot.

SUMMARY

Therefore, among other features, the invention improves foot support in the boot or, in other words, reduces or even eliminates undesired foot displacements within the boot, especially in the transverse and/or vertical direction.

In addition, the invention provides for a more comfortable boot, in terms of less user fatigue, whether in a static mode or in a dynamic mode. Indeed, whether at rest or in motion, the user advantageously senses forces that are comfortable, such as those occurring when skiing, hiking, or while engaged in other sporting activities.

Furthermore, the invention optimizes the transmission of steering forces or sensory information between the user and an element outside of the boot, such as the ground or a sports apparatus.

To this end, the invention provides a boot having an outer sole assembly and an upper, the boot extending lengthwise from a heel to a front end, widthwise between a lateral portion and a medial portion, and heightwise from the outer sole assembly to an upper end, the boot having an opening for foot insertion, and including a reinforcement which is integral with the upper and is more rigid than the remainder of the upper, at least in the region of the instep, the reinforcement including a lateral wall and/or a medial wall extending over a reduced length of the boot, at least plumb with, the instep, the boot including a transverse linkage provided to tighten the instep zone, the linkage extending from the lateral portion to the medial portion.

The boot according to the invention includes a linkage that includes a first subdivision extending in the longitudinal direction of the boot, over a distance between 25% and 70% of the length of the boot.

The transverse linkage is tensioned and reversibly maintained tensioned by any known device. For example, the transverse linkage can include a lateral portion and a medial portion, as well as a reversible tightening mechanism.

Therefore, in the boot according to the invention, the linkage longitudinally extends the transverse tightening action. As a result, foot support pressures are distributed over a greater length in relation to both a subdivision of the tarsus and a subdivision of the metatarsus. This pressure distribution, in the direction increasing lengthwise, prevents or substantially reduces a tilting effect of the foot in the upper, in relation to a transverse axis. This also means that the alternate lifting movements of the posterior tarsus and of the metatarsus are prevented or very limited. This effect is obtained by the difference in relation to the prior art, in which a narrower transverse linkage sometimes acts as a pivot axis for the foot in the upper.

Thus, the invention advantageously improves foot support, and thereby reduces or even eliminates undesired displacements of the foot within the boot. The risks of injury therefore are avoided or even completely eliminated.

Another advantage of the invention is greater comfort of the foot in the boot, especially in terms of reduced user fatigue, whether in a static mode or in a dynamic mode.

The invention also advantageously improves the transmission of steering impulses or of sensory information between the user and an element outside of the boot, such as the ground or a sports apparatus.

BRIEF DESCRIPTION OF DRAWINGS

Other characteristics and advantages of the invention will be better understood from the description which follows, with reference to the annexed drawings illustrating, by way of non-limiting embodiments, how the invention can be embodied, and in which:

FIG. 1 is a perspective front view of a boot according to a first embodiment of the invention, which shows a lateral portion, in the case in which the transverse linkage tightens the upper;

FIG. 2 is a perspective front view of the boot of FIG. 1, which shows a medial portion, in the case in which the transverse linkage is open;

FIG. 3 is a view on the medial side of the boot of FIG. 1;

FIG. 4 is a perspective front view of a reinforcement of the boot of FIG. 1;

FIG. 5 is a view on the lateral side of the boot of FIG. 1;

FIG. 6 is a perspective front view of a boot according to a second embodiment of the invention, which shows a medial portion, in the case in which the transverse linkage is open;

FIG. 7 is a perspective front view of the boot of FIG. 6, which shows a lateral portion, in the case in which the transverse linkage tightens the upper.

DETAILED DESCRIPTION

The first embodiment described below relates more particularly to boots constructed for the practice of cross-country skiing or telemark skiing. However, the invention is applicable to other fields such as those mentioned above.

The first embodiment is described below with reference to FIGS. 1-5.

As shown in FIG. 1, a cross-country ski boot 1 is provided to receive the foot of a user.

As known, the boot 1 includes an outer sole assembly 2 and an upper 3 extending upwardly beyond the outer sole assembly. The boot 1 extends lengthwise from a rear end, or heel 4, to a front end, or tip 5, and widthwise between a lateral portion 6 and a medial portion 7.

As shown, the upper 3 includes a lower portion 10, provided to surround the foot, and a top portion 11, adapted to surround the ankle. However, an upper having only a lower portion is within the scope of the invention.

According to the first illustrated embodiment, the boot 1 extends heightwise from the outer sole assembly 2 to an upper end 12, i.e., up to the free end of the top portion 11 or of the upper 3.

The boot 1 is structured so as to enable proper bending of the leg or a good rolling movement of the foot, as well as the transmission of sensory information or steering impulses. Therefore, the upper 3 is relatively flexible. The outer sole assembly can be relatively rigid, or it can be much more flexible.

As seen more clearly in FIG. 2, the boot 1 includes a lateral quarter 15 and a medial quarter 16. The quarters 15, 16 are adapted to cover the foot and, as such, are the constituent elements of the lateral portion 6 and medial portion 7, respectively.

The quarters 15, 16 are affixed to the outer sole assembly by means of known techniques, such as an adhesive, stitching, or any other equivalent technique. The quarters 15, 16 are arranged such that the boot 1 has an opening 17 for foot insertion. The opening 17 extends from the upper end 12 of the boot to the front end 5. On the side of the upper end 12, the opening 17 has an upper subdivision 18 constructed to allow the foot to pass through, and also to surround the ankle after the foot has been inserted in the boot. The opening 17 has a lower subdivision 19 which enables the size of the opening and the size of the fitting volume to vary, in the area of the instep, between the upper end 12 and the front end 5. The upper 18 and lower 19 subdivisions are co-extensive with one another.

The heel 4 corresponds to the rear end of the upper 3, but also, by extension, to the portion of the upper that is located immediately above the outer sole assembly, and is plumb with the upper subdivision 18 of the opening top 17. The heel 4 of the boot envelops the heel of the user.

The upper 3 includes a tongue 20, which is arranged between the lateral quarter 15 and the medial quarter 16, in the area of the lower subdivision 19 of the opening 17, in order to provide the upper 3 with continuity. However, the tongue could be omitted, in which case, the quarters 15, 16 can be spaced apart or overlapped. Alternatively, the quarters could be connected to one another via a gusset.

In addition, the boot 1 optionally includes a flap 25 provided to reversibly cover the lower subdivision 19 of the foot insertion opening 17. The flap 25 extends from one of the quarters 15, 16 to the other to improve the imperviousness of the boot

According to the first embodiment, the flap 25 is fixedly connected to the lateral quarter 15. The flap 25 covers the foot insertion opening by being folded over the latter and over the medial quarter 16. Although that it is not the case here, a reversible closure can be provided, which makes it possible to also affix the flap 25 to the medial quarter 16. In this case, the reversible closure includes a slide fastener. However, any other structure could be provided to obtain closure. For example, a series of snap fasteners could be used.

The boot 1 further includes a tightening device 30, provided to reduce the opening reversibly. In other words, the tightening device 30 makes it possible to tighten the upper 3 reversibly.

As is known to one of ordinary skill in the art, the tightening device 30 includes, for example, a first linkage 31, a second linkage 32, as well as connections 33 for the linkages to the upper 3. Each linkage runs from one quarter 15, 16 to the other in the area of the lower subdivision 19. This arrangement makes it possible to reversible tighten the upper 3 toward the instep, in the area of the lower subdivision 19 of the opening 17. Thus, it is possible to apply a tightening force on the foot of the user. The boot 1 is provided with a removable blocking mechanism in order to keep the device 30, and therefore of the upper 3, tightened. This removable blocking mechanism, not described in detail here, also provides quick release.

Any other means for maintaining the tightening at a certain force level could be provided. In particular, the blocking mechanism could be eliminated and replaced with a knot, that is, the linkages can be tied into a knot.

As shown in all FIGS. 1 to 5, the boot 1 includes a reinforcement 40 (shown in isolation in FIG. 4) which is integral with the upper and is more rigid than the remainder of the upper 3, at least in the region of the instep, the reinforcement 40 including a bottom portion 41, a lateral wall 42 and/or a medial wall 43, the reinforcement 40 extending plumb with, as far forward as, the flexion crease and/or the instep. The reinforcement 40 extends here to the outside of the structure of the upper, but it could alternatively extend further within the structure. Alternatively, the boot includes a transverse linkage 50 provided to tighten the instep zone, the linkage 50 extending from the lateral portion 15 to the medial portion 16, outside of the remainder of the upper.

The bottom portion 41 of the reinforcement 40 supports the foot, directly or indirectly. Consequently, the lateral and medial walls 42, 43 are opposite the lateral and medial zones of the foot. Thus, in view of the relative rigidity of the reinforcement 40 and the relative rigidity of the upper 3 in the region of the instep, as well as the location of the transverse linkage 50 provided to tighten the latter, the foot is maintained pressing directly or indirectly on the bottom portion 41 and on one or both walls 42, 43 of the reinforcement. This ensures that the foot is held securely in the vertical direction and in the transverse direction.

With particular reference to FIG. 4, according to the first embodiment of the invention, the reinforcement 40 includes not only the bottom portion 41, the lateral wall 42 and the medial wall 43, but also a rear wall 44. More specifically, the lateral wall 42, rear wall 44, and medial wall 43 are co-extensive with one another to form a continuous wall 45, extending from the heel 4 toward the front end 5 of the boot. The lateral wall 42 has a lateral top 46 and a front end 47. Similarly, the medial wall 43 has a medial top 48 and a front end 49. Therefore, the continuous wall 45 extends ascends and then descends, as it extends from the heel 4 to the front end 5. In fact, the lateral top 46 and medial top 48 are plumb with the upper subdivision 18 of the foot insertion opening 17. This enables a better transverse support of the ankle.

Still according to the first embodiment of the invention, the bottom portion 41 of the reinforcement extends from the heel 4 to the front end 5 of the boot, beyond the lateral and medial front ends 47, 49 of the lateral and medial walls 42, 43 of the reinforcement 40. In other words, the lateral and medial walls 42, 43 of the reinforcement 40 extend over a reduced length of the boot. More specifically, the lateral and medial walls 42, 43 extend from the heel 4 to a position plumb with the instep, i.e., in the area of the tightening device 30. As a result, the heel and instep of the user's foot are received in a rigid hollow form demarcated by the bottom portion 41 and the wall 45, and the front end of the foot is received on a flat portion of the reinforcement 40, at the front of the lateral and medial walls 42, 43. In fact, this flat portion enables bending of the forefoot, or a rolling movement of the foot, especially in the area of the toes.

The lateral and medial walls 42, 43 are substantially opposite each other, which, as seen more clearly below, makes it easier to position the transverse linkage 50 on the boot.

The reinforcement 40 is made from known materials and methods. In a particular structural variation, the bottom portion 41 and the walls 42, 43, 44 form a unitary element. This element can include fibers of synthetic and/or natural materials embedded in a matrix. For example, carbon and/or glass fibers, impregnated in thermosetting or thermoformable resin, make the reinforcement 40 highly rigid, meaning more rigid than the remainder of the upper, in particular the quarters 15, 16.

Alternatively, other materials, for example, a plastic loaded with particles and/or cut fibers, can be provided for the reinforcement 40. In this case, the reinforcement 40 is obtained by molding, injection, or any equivalent methods.

According to the invention, the transverse linkage 50 includes a first subdivision 51 extending in the longitudinal direction of the boot, over a distance between 25% and 70% of the length thereof. This arrangement corresponds to an extended cooperation of the linkage with the remainder of the upper. Thus, the tightening pressure is distributed over a greater length. It follows advantageously that foot support in the boot is better. No undesired movements of the foot, or no more than insignificant movements of the foot, are observed in the boot. Therefore, comfort and steering precision are both improved.

According to the first embodiment, and in a non-limiting manner, as can be seen in FIG. 3, the first subdivision 51 of the linkage 50 extends from the posterior tarsus to the metatarsus. The posterior tarsus is the heel of the foot, whereas the metatarsus extends from the tarsus to the base of the toes. This range, which corresponds to a distance between 50% and 70% of the length L of the boot 1, enables the linkage 50 to tighten the upper 3 opposite the most rigid portion of the foot, particularly in bending. In fact, the bones of the foot significantly limit bending along a transverse axis of the metatarsal in relation to the tarsus. Therefore, the foot support being longitudinally extended protects the foot from excessive forces, with respect to bending. Consequently, fatigue associated with the use of the boot is reduced.

In parallel, tightening the transverse linkage 50 maintains the flap 25 facing the foot insertion opening 17, in the area of the lower subdivision 19, and on the medial quarter 16.

According to the first embodiment, the first subdivision 51 is medial. This arrangement promotes extensive tightening of the medial portion of the foot. As a result, the transmission of steering impulses is facilitated on the medial side of the foot. This possibility improves the skating step, especially in cross-country skiing.

An alternative arrangement, in which the first subdivision 51 is lateral, can be provided. In this case, the transmission of forces is improved on the lateral side of the foot, which is suitable, for example, for snowplow braking.

Still according to the first embodiment, the first subdivision 51 is affixed directly to the reinforcement 40, which enables the foot to be tightened optimally toward the reinforcement 40, whether on the medial side, if the first subdivision 51 is medial, or on the lateral side, if the first subdivision 51 is lateral.

The reinforcement 40 is located outside of the upper 3 for better foot comfort. Indeed, as a result, more flexible layers of the upper are positioned between the foot and the reinforcement 40. The reinforcement can also be positioned farther inside the upper 3, or completely inside the upper, especially if performance is preferred over comfort.

To cooperate with the reinforcement 40, the transverse linkage 50 is structured and arranged so as to be reversibly tightened between the lateral and medial walls 42, 43. As shown in FIGS. 1 to 5, the transverse linkage 50 includes, for example, a first portion 55, or medial portion, a second portion 56, or lateral portion, as well as a first mechanism 57 for removably connecting the portions. The transverse linkage 50 is affixed to at least a portion of the reinforcement 40.

According to the first embodiment of the invention, the first subdivision 51 of the linkage 50 is integral with the first portion 55, and the first subdivision 51 has a generally triangular shape. In fact, the first subdivision 51 widens in a direction towards the outer sole assembly 2, i.e., in the longitudinal direction, as it extends from the opening 17 to the outer bottom assembly. This makes it possible to distribute the tightening pressure over a greater length on the medial side of the foot. This arrangement is well-suited for transverse thrusts of the leg, for example when practicing the skating step in cross-country skiing.

In a non-limiting fashion, the first subdivision 51 includes an array of three branches, or arms, namely a rear branch 61, a central branch 62, and a front branch 63. The branches 61, 62, 63 form a fasciculus, with the branches widening in a direction towards the outer sole assembly 2, in a stay-like fashion, for optimal tension distribution. The array of branches extends from the foot insertion opening 17 and widens toward the outer sole assembly. Consequently, the tightening pressures are more balanced along the first subdivision, and foot support is therefore more uniform along the tarsus and metatarsus.

Although the number three is a satisfactory number of branches, not only for balancing the tensions but also for enabling the subdivision 51 to properly follow the contours of the portions of the upper which it covers, a different number of branches can be provided. The first subdivision 51 can even have a continuous, non-perforated surface, or a structure that is perforated but organized differently than via an array of branches.

As shown clearly in FIG. 3, a rear edge 64 of the first subdivision 51 forms, together with a plane P tangent to the outer sole assembly 2, i.e., a plane on which the outer sole assembly 2 can be supported, an angle α whose value is between 35 and 70 degrees. The rear edge 64 demarcates the first subdivision 51, and therefore also the rear branch 61, toward the rear of the boot and in a direction away from the outer sole assembly 2. This value of the angle α causes the virtual extension of the rear edge 64 to intersect the plane P in the area of the rear end 4, or even at a distance from the rear end 4 in a rearward direction. It follows advantageously that the transverse linkage 50 is adapted to tighten the posterior tarsus, or the heel of the foot, in a tightening direction, i.e., in a direction toward the outer sole assembly 2 and/or toward the medial portion 7 of the boot.

Furthermore, a front edge 65 of the first subdivision 51 forms, together with the plane P tangent to the outer sole assembly 2, an angle β whose value is between 60 and 85 degrees. The front edge 65 demarcates the first subdivision 51, and therefore also the front branch 63 toward the front of the boot. This value of the angle β locates the front edge 65 in the area of the metatarsus, in the vicinity of the articulations which connect the metatarsus to the toes. It follows advantageously that the transverse linkage 50 is capable of tightening the metatarsus in a direction towards the outer sole assembly 2 and/or the medial portion 7 of the boot.

On the other side of the first subdivision 51, as shown clearly in FIG. 5, the second portion 56 of the linkage 50 includes a strip 66 having a width W between 5% and 20% of the length L of the boot. In combination with the widened first subdivision 51 of the first portion 55, the configuration of the second portion 56 gives preference to a stronger tightening on the medial side of the boot. This makes the boot more suitable for the practice of the skating step.

In a non-limiting fashion, the second portion 56 is affixed directly to the reinforcement 40, in fact to the lateral wall 42 of the reinforcement.

In addition, the mechanism 57 for connecting the first and second portions 55, 56 is comprised, for example, of a ratchet tightening mechanism. The mechanism is not described in detail here, as it is well known to one of ordinary skill in the art, although the disclosure of U.S. Patent Application Publication No. US 2009/0119952 is incorporated by reference in its entirety particularly for its disclosure of such a mechanism. The tightening mechanism 57 is affixed to the second portion 56 and, as a result, the first portion 55 includes a rack 70. The rack joins the three branches 61, 62, 63 of the first subdivision 51, for better transmission of the tightening forces by the linkage.

The second embodiment of the invention is illustrated below with reference to FIGS. 6 and 7. For reasons of convenience, the elements shared with the first embodiment are designated by the same reference numerals. Thus, only the differences are highlighted.

Therefore, the second embodiment is directed to a boot 1 that includes an outer sole assembly 2, an upper 3, and a transverse linkage 80.

What is specific to the second embodiment is the arrangement of the linkage 80. The linkage includes a first subdivision 81 extending in the direction of the length L of the boot 1, over a distance 1 between 25% and 70% of the length L of the boot. But the first subdivision 81 here is lateral.

The link 80 includes a first portion 85 or lateral portion, a second portion 86, or medial portion, and mechanism 87 for connecting the portions.

The first portion 85 includes a rear branch 91, a center branch 92, and a front branch 93. The connecting mechanism 87 is affixed to the first portion 85. The second portion 86 is comprised of a rack adapted to cooperate with the connecting mechanism 87.

In any case, the invention is made from materials and according to techniques of implementation known to one of ordinary skill in the art.

The invention is not limited to the embodiments described above, and includes all technical equivalents that fall within the scope of the claims that follow.

In particular, in any case, the architecture of a transverse linkage can be inverted, in the sense that the specificities related to a lateral portion can be located on a medial portion and vice versa.

Thus, the specificities related to one of the lateral and medial portions can be located on each of the portions. For example, the linkage can be provided to include a second subdivision, i.e., in addition to the first which extends in the longitudinal direction of the boot over a distance between 25% and 70% the length thereof.

In addition to the foregoing, the invention disclosed herein by way of exemplary embodiments suitably may be practiced in the absence of any element or structure which is not specifically disclosed herein. 

1. A boot comprising: an outer sole assembly; an upper extending upwardly beyond the sole assembly; a length extending in a longitudinal direction between a heel and a tip, a width extending transversely between a lateral portion and a medial portion, and a height extending between the outer sole assembly and an upper end; an opening for receiving a wearer's foot; a reinforcement integral with the upper and more rigid than a remainder of the upper; at least in an instep region, the reinforcement comprising a lateral wall and/or a medial wall extending less than an entirety of the length of the boot and extending forwardly at least as far as plumb with the instep; a transverse linkage structured and arranged to tighten an instep zone, the linkage extending from the lateral portion to the medial portion; the linkage comprising a first subdivision extending in the longitudinal direction of the boot, over a distance between 25% and 70% of the length of the boot.
 2. A boot according to claim 1, wherein: the first subdivision of the linkage extends from the posterior tarsus to the metatarsus.
 3. A boot according to claim 1, wherein: the first subdivision is medial.
 4. A boot according to claim 1, wherein: the first subdivision is lateral.
 5. A boot according to claim 1, wherein: the first subdivision is affixed directly to the reinforcement.
 6. A boot according to claim 1, wherein: the reinforcement is located on an outside of the upper.
 7. A boot according to claim 1, wherein: the reinforcement comprises the lateral wall and the medial wall.
 8. A boot according to claim 1, wherein: the transverse linkage comprises a first portion; the first subdivision is integral with of the first portion; the first subdivision has a generally triangular shape.
 9. A boot according to claim 8, wherein: the first subdivision comprises three branches.
 10. A boot according to claim 8, wherein: a rear edge of the first subdivision forms, together with a plane tangent to the outer sole assembly, an angle having a value between 35 and 70 degrees.
 11. A boot according to claim 8, wherein: a front edge of the first subdivision forms, together with a plane tangent to the outer sole assembly, an angle having a value between 60 and 85 degrees.
 12. A boot according to claim 8, wherein: the transverse linkage comprises a second portion and a connecting mechanism provided to removably connect the second portion to the first portion.
 13. A boot according to claim 12, wherein: the second portion comprises a strip; the width of the strip is between 5% and 20% of the length of the boot.
 14. A boot according to claim 12, wherein: the linkage comprises a second subdivision extending in the longitudinal direction of the boot, over a distance between 25% and 70% of the length of the boot.
 15. A boot according to claim 1, further comprising: a flap provided to cover the foot insertion opening. 